The invention relates to an antilipemic composition and in particular to a composition for lowering cholesterol.
As outlined in a recent publication [Facts About Cholesterol: The Plague of Plaque, FDA Consumer magazine, January-February 1999], cholesterol, C27H45OH, is a monohydric alcohol, a sterol, widely distributed in animal tissues. It can be synthesized in the liver and is a normal constituent of bile. It is the principal constituent of most gallstones. It is important in metabolism, serving as a precursor of various steroid hormones (e.g., sex hormones, adrenal corticoids). In most individuals, however, an elevated blood level of cholesterol constitutes an increased risk of developing coronary heart disease (CHD). Scientific evidence has established that lowering definitely elevated blood cholesterol (specifically, blood levels of low-density lipoprotein cholesterol) reduces the risk of heart attacks due to CHD.
Cholesterol is needed for some important body functions, but when present in excessive amounts, it can injure blood vessels and cause heart attacks and stroke. The body needs cholesterol for digesting dietary fats, making hormones, building cell walls, and other important processes. The bloodstream carries cholesterol in particles called lipoproteins that are like blood-borne carriers delivering cholesterol to various body tissues to be used, stored or excreted. But too much of this circulating cholesterol can injure arteries, especially the coronary ones that supply the heart. This leads to accumulation of cholesterol-laden xe2x80x9cplaquexe2x80x9d in vessel linings, a condition called atherosclerosis. If a blood clot completely obstructs a coronary artery affected by atherosclerosis, a heart attack (myocardial infarction) or death can occur.
Lipoproteins are conjugated proteins consisting of simple proteins combined with lipid components: cholesterol, phospholipid, and triglyceride. Most plasma lipids do not circulate in an unbound state but are chemically linked with proteins. Analysis of their concentrations and proportions in the blood can provide important clues as to their role in certain diseases, particularly cardiovascular abnormalities, hypertension, atherosclerosis, and coronary artery disease. Lipoproteins are classified as very low-density (VLDL), low-density (LDL), intermediate-density (IDL) and high-density (HDL). It is thought that individuals with high blood levels of HDL are less predisposed to coronary heart disease than those with high blood levels of VLDL or LDL.
Two types of lipoproteins and their quantity in the blood are main factors in heart disease risk:
Low-density lipoprotein (LDL)xe2x80x94This xe2x80x9cbadxe2x80x9d cholesterol is the form in which cholesterol is carried into the blood and is the main cause of harmful fatty buildup in arteries. The higher the LDL cholesterol level in the blood, the greater the heart disease risk.
High-density lipoprotein (HDL)xe2x80x94This xe2x80x9cgoodxe2x80x9d cholesterol carries blood cholesterol back to the liver, where it can be eliminated. HDL helps prevent a cholesterol buildup in blood vessels. Low HDL levels increase heart disease risk.
One of the primary ways LDL cholesterol levels can become too high in blood is through eating too much of two nutrients: saturated fat, which is found mostly in animal products, and cholesterol, found only in animal products. Saturated fat raises LDL levels more than anything else in the diet. Several other factors such as heredity, weight, exercise, age and gender, and stress also affect blood cholesterol levels.
Cholesterol levels may be decreased by several factors, including diet, avoiding smoking, and avoiding anabolic steroids. Drugs commonly used to control cholesterol include lovastatin, niacin, gemfibrozil, clofibrate, probucol, and bile-acid resins (cholestyramine, colestipol). The decision of which drug to prescribe is based on factors such as degree of cholesterol lowering desired, side effects, and cost.
A number of substances have been applied to reduce cholesterol levels in blood. One of the early therapies involved heparin, a polysaccharide isolated from natural sources. However, the isolation process is costly and heparin therapy is therefore rather expensive at efficient doses. This led to the introduction of sulphated polysaccharides known as heparinoides. The additional sulphatation and the presence of the OSO3H groups brought about a lower efficiency and a higher toxicity compared to heparin.
Another group of polymers applied as antilipemics have been anion exchange resins of varying degree of basicity, exchanging Cl-ions for anions of bile acids. Cholestyramine and colestipol bind bile acids in the intestine and prevent their recycling through the liver. Because the liver needs cholesterol to make bile, it increases its uptake of cholesterol from the blood. These drugs are, in most cases, not resorbed from the gastrointestinal tract, but can adversely affect resorption of other drugs. Due to the rather high daily doses (up to 30 g) they may also cause gastric problems.
Antilipemic properties have also been observed for certain hormones such as gestagens. Their complex hormonal activity precludes, however, their common use in antilipemic therapy.
Nicotinic acid (niacin) lowers total and LDL cholesterol and raises HDL cholesterol. It also can lower triglycerides. Because the dose needed for treatment is about 100 times more than the recommended daily allowance for niacin and thus can potentially be toxic, the drug must be taken under a doctor""s care.
Fibric acid derivatives such as gemfibrozil and fenofibrate can also increase HDL levels, but are used mainly to lower triglycerides.
The most prominent cholesterol drugs are in the statin family, an array of powerful treatments that includes lovastatin, fluvastatin, pravastatin, simvastatin), cervastatin, and atorvastatin. Statins work by interfering with the cholesterol-producing mechanisms of the liver and by increasing the capacity of the liver to remove cholesterol from circulating blood. Adverse side effects have also been reported recently for antilipemic drugs based on statins such as fluvastatin.
The invention in particular involves the use of polyanhydroglucuronic acids and salts thereof The term polyanhydroglucuronic acid and salts there of as used herein also includes copolymers thereof, especially with anhydroglucose. This is hereinafter referred to as PAGA.
Co-pending patent application PCT IE98/00004 describes particular polyanhydroglucuronic acids and salts thereof and a method of preparing such compounds. In particular therefore, the term polyanhydroglucuronic acids and salts thereof includes the acids and salts referred to in this co-pending application.
We have now found an important antilipemic effect, comparable with that of statins, in non-sulphated polysaccharides containing glucuronic acid in the polymer chain. Glucuronoglucanes, notably those bound with 1,4 xcex2 glycosidic bonds in the form of PAGA as prepared, particularly, according to PCT IE/98/00004, their salts, complex salts, and intermolecular complexes thereof with cationic polymer counterions such as, notably, gelatine or chitosan, when applied perorally, preferably in the form of tablets, pellets, granules, or microspheres, display a significant cholesterol lowering activity at relatively low daily doses of 15 to 100 mg per kg body weight.
In tests on volunteers it has been observed that the effect of increasing HDL cholesterol level, and reducing both LDL/ VLDL and total cholesterol levels was comparable with a control group of patients treated with fluvastatin with no adverse side effects reported.
It may be hypothesised that the mechanism of this effect is related to the increased supply of glucuronic acid and their oligomers to the organism during absorption and degradative clearance of the orally administered glucuronoglucane.
One advantage of the therapy based on the invention is due to the inherent biocompatibility, lack of toxicity and virtual absence of adverse side effects inherent to PAGA salts and intermolecular complexes, especially when prepared according to the method of, and as explained in, PCT IE/98/00004. This together with the low doses required reduce the potential risks to the patient compared with other types of antilipemic drugs.
A final advantage resides in the fact that PAGA salts and intermolecular complexes, especially when prepared according to the method of the earlier PCT IE/98/00004 can, in addition to their own therapeutic function, simultaneously serve as a vehicle for other antilipemic agents with potential synergic effects such as notably phospholipides, e.g. soya or egg derived lecithins, xcex1-tocoferol, or ascorbic acid.
According to the invention there is proved an anlilpemic composition including a biocompatible anionic polysaccharide material containing non-sulphated glucuronic acid.
Preferably the polysaccharide is derived from a starch, cellulose or gum, or is of microbial origin.
In a particularly preferred embodiment the polysaccharide material is polyanhydroglucuronic acid, biocompatible salts thereof, copolymers thereof or a biocompatible intermolecular complex polymer thereof.
In an embodiment of the invention the biocompatible intermolecular polymer complex is a complex of:
an anionic component comprising a linear or branched polysaccharide chain containing glucuronic acid; and
a non protein cationic component comprising a linear or branched natural, semi-synthetic or synthetic oligomer or polymer.
Preferably at least 5% of the basic structural units of the anionic component are glucuronic acid.
In one embodiment the cationic component contains nitrogen that either carries a positive charge or wherein the positive charge is induced by contact with the polysaccharidic anionic component.
In this case preferably the cationic component is selected from derivatives of acrylamide, methacrylamide and copolymers thereof.
Preferably the cationic component is selected from polyacrylamide, copolymer of hydroxyethylmethacrylate and hydroxypropylmetacrylamide, copolymers of acrylamide, butylacrylate, maleinanhydride and/or methylmetacrylate.
The cationic component may be a cationised natural polysaccharide.
In this case preferably the polysaccharide is a starch, cellulose or gum. The gum is preferably guargumhydroxypropyltriammonium chloride.
In another embodiment the cationic component is a synthetic or semi-synthetic polyamino acid.
Preferably the cationic component is polylysin, polyarginin, or xcex1,xcex2-poly-[N-(2-hydroxyethyl)-DL-aspartamide].
Alternatively the cationic component is a synthetic anti-fibrinolytic. The anti-fibrinolytic may be a hexadimethrindibromide (polybren).
In another embodiment the cationic component is a natural or semi-synthetic peptide.
Preferably the peptide is a protamine, gelatine, fibrinopeptide, or derivatives thereof.
Alternatively the cationic component is an aminoglucane or derivatives thereof.
In this case the aminoglucane may be fractionated chitin or its de-acetylated derivative chitosan.
The aminoglucane may be of microbial origin or is isolated from the shells of arthropods such as crabs.
In an particularly preferred embodiment the anionic component is polyanhydroglucuronic acid [PAGA].
Preferably the polyanhydroglucuronic acid and salts thereof contain in their polymeric chain from 8 to 30 per cent by weight of carboxyl groups, at least 80 per cent by weight of these groups being of the uronic type, at most 5 per cent by weight of carbonyl groups, and at most 0.5 per cent by weight of bound nitrogen.
Ideally the polyanhydroglucuronic acid and salts thereof contain in their polymeric chain at most 0.2 per cent by weight of bound nitrogen.
The molecular mass of the polymeric chain of the anionic component is preferably from 1xc3x97103 to 3xc3x97105 Daltons.
Ideally the molecular mass of the polymeric chain of the anionic component ranges from 5xc3x97103 to 1.5xc3x97105 Daltons.
In one embodiment the content of carboxyl groups is in the range of from 12 to 26 per cent by weight, at least 95 per cent of these groups being of the uronic type.
Preferably the anionic component contains at most 1 per cent by weight of carbonyl groups.
In a preferred embodiment the carbonyl groups are intra- and intermolecular 2,6 and 3,6 hemiacetals, 2,4 hemialdals and C2-C3 aldehydes.
In another embodiment the cationic component is gelatine.
In a further embodiment the cationic component is chitosan.
The composition may include at least one biocompatible biologically active substance.
The composition may include at least one pharmaceutically active adjuvant.
The adjuvant may be an antilipemic agent.
The antilipemic agent may be a phospholipid.
The composition may be in a form for oral administration such as in the form of a tablet, pellet, capsule, granule, or microsphere.
We have now found that by preparing polymeric intermolecular complexes (IMC) of glucuronoglucanes, notably microdispersed PAGA, prepared especially according to PCT IE 98/00004 it is possible to enhance the haemostatic effect of the final products on this basis and the properties of the temporary wound cover formed after the haemostasis is achieved such as its flexibility and resistance to cracking on movable parts of the body.
It is also possible to upgrade physicomechanical properties of the final products on this basis. Such IMCs make it possible to prepare application forms whose manufacture from a pure PAGA or their simple salts is extremely difficult. Such application forms includes non-woven textile-like structures or polymeric films. To modify or upgrade the physical mechanical properties it is sufficient to use even a relatively small amount of polymeric counterion while it is possible to obtain suitable application properties within a broad concentration range of the components. The ratio of the glucuronoglucane to polymeric counterion can be 0.99:0.01 to 0.01:0.99.
Another advantage of glucuronoglucane based IMCs is the possibility to control their biological properties such as varying the degree of haemostatis, resorption time, or immunomodulative properties, and the like.
Polymeric cations suitable to form IMCs with glucuronoglucanes prepared for example according to PCT IE 98/00004 may roughly be subdivided to the following groups:
1. Synthetic biocompatible nitrogen-containing oligomers and polymers.
a) Derivatives of acrylamide and methacrylamide and their copolymers [such as polyacrylamide, copolymer of hydroxyethylmetacrylate and hydroxypropylmetacrylamide, copolymer of acrylamide, butylacrylate, maleinanhydride, and methylmetacrylate, and the like], or else cationised natural polysaccharides such as starches, celluloses, or gums such as guargumhydroxypropyltriammonium chloride.
b) Synthetic or semi-synthetic polyaminoacids such as polylysin, polyarginin, xcex1,xcex2-poly-[N-(2-hydroxyethyl)-DL-asparamide. Synthetic antifibrinolytics hexadimethrindibromide (polybren) can also be included in this group.
2. Natural or semi-synthetic peptides such as gelatine, protamines, or fibrinopeptides, and their derivatives.
3. Natural aminoglucanes such as fractionated chitin and its de-acetylated derivative chitosan, of microbial origin or isolated from the shells of arthropods such as crabs.
In preparing IMCs on the basis of PAGA according to the invention these three groups of substances can be combined to obtain required properties of the final product.
In general it can be said that IMCs using substances from 1a and 1b would preferably be used to prepare various types of highly absorbant biocompatible dressing materials in the form of nonwovens, films, plasters, and pads.
IMCs using the substances from 2 and 3 may serve as efficient haemostatic agents for internal applications in the microfibrillar form, in the microdispersed form as dusting powders, in the form of films, granules, tablets or non-woven textile-like structures. Those preparations also display antiadhesive properties.
We have also found out that in the form of film-like cell culture matrices the latter IMCs incorporating PAGA and salts thereof as prepared according to PCT IE 98/00004 have a favourable effect on the growth of fibroblasts and keratinocytes.
While it is also possible to create IMCs using structural scleroproteins of the collagen type as disclosed in WO 9800180A, it is preferable to use the above mentioned groups of substances because of the possibility of contamination of the final product by telopeptides, viruses or pyrogens. Collagen can affect in an uncontrolled manner, the immune response of the organism because formation of antibodies can be provoked by any portion of the collagen structure even though the main determinants occur in the terminal regions of the collagen macromolecule. Removal of telopeptides only partially solves the antigenicity problem (Michaeli et al: Science, 1969, 166, 1522).
By preparing IMCs according to the invention it is possible to essentially enhance properties of the originally prepared glucoronoglucanes such as 1,4 xcex2 PAGA. For instance an intermolecular complex salt of PAGA and gelatine in one single production step can be used to prepare final products in the form of a non woven, film, microdispersed granules, or dispersions. In contrast to collagen, suitably hydrolysed gelatine is well tolerated, has no toxicity or side effects and it is a much less costly raw material. We have found out that this complex has very good haemostatic properties being about 40% higher than the original PAGA calcium sodium salt. This is despite the fact that the gelatine itself only displays a haemostatic effect after an addition of thrombin [Schwartz S. I. et al.: Principles of Surgery, St. Louis: McGraw Hill Colo., 1979, p. 122-123]. In this case the absorption in the organism can be controlled by changing the composition of the complex within the range from tens of hours to several months. With an advantage this complex with a higher haemostatic efficiency can be used as an embolisation or microembolisation product. It can also be used to prepare haemostatic layers of highly absorbent multi-layer dressings or resorbable plasters, though more costly polybren or protamines could also be applied.
An important advantage of these IMCs is the fact that the compounds can be prepared within a single manufacturing operation using the hydrolytic process described in PCT IE 98/00004 which makes these products cost effective.
These IMCs can further be modified by biologically active and/or biologically acceptable substances. Because the IMCs prepared by the present procedure are either of a microdispersed or microfibrillar nature, the active substances tend to be bound uniformly and also are uniformly released in the organism without the need for other adjuvants such as microcrystalline waxes or stearates. However, the addition of such adjuvants is not excluded.
Biologically active substances which can be incorporated into the IMC may involve, for instance, antibiotics carrying at least a weak positive charge in the molecule such as cephalosporins (cephotaxin), arninoglycosides (neomycin, gentamycin, amikacin), penicillins (tikarcilin) or macrolides (erythromycin, clarithromycin) and the like.
In cases where the calcium/sodium salt of PAGA or its IMC complexes according to the invention are used as microembolisation or embolisation agents in regional chemotherapy of malign tumours, suitable types of cytostatics such as adriamycin or derivatives of 1,4-diaminoanthrachinone can be incorporated. It is also possible to use the IMCs as detaching ligands for platinum(II) based cytostatics.
Biologically acceptable substances used for modification of the IMCs include, for instance, glycerol and its polymers (polyglycerols); mono, di, and certain triglycerides; polyethyleneglycols; monopropyleneglycol; block copolymers of polyethyleneoxides and polypropyleneoxides (Pluronic); starches; cyclodextrines; polyvinylalcohols; cellulose and its derivatives; in general, substances that, in the concentrations used, are not irritating or toxic for the living organism while being capable of further optimising the physicomechanical properties of the final product based on the IMCs according to the invention.
The invention will be more clearly understood from the following description thereof given by way of example only.